Re: luaL_checklstring over nil raises exception

[Patrick Rapin <toupie300@...>]

The library function luaL_checkstring, like all luaL_check* series,
return a valid value if the type is the expected one, or signals an
error when the type is not correct.
If you have compiled Lua in C++ mode without defining LUA_USE_LONGJMP,
Lua uses C++ exceptions for its errors. In this case, what you see if
perfectly normal.